Escherichia coli (ATCC 35218), a surrogate for Salmonella, was maintained on tryptic soy agar (TSA; Becton, Dickinson and Company, Franklin Lakes, NJ) at 4 C. The E. coli was cultured in tryptic soy broth (Becton, Dickinson and Company) with shaking at 37 C for 16e18 h